On Mon, 2005-11-07 at 18:43, Tom Lane wrote: [snip] > If it doesn't have a value for the parameter, it'll assume 10% of table > rows, which is what it's done for a long time if the LIMIT isn't > reducible to a constant.
Is 10% a reasonable guess here ? Here we use limit in combination with prepared statements to get something like less than 1% of the table. There are no exceptions to that in our code... even if the limit amount is a parameter. Furthermore, the limit amount is always a small number, usually ~ 100, but never more than 1000. So in my case, we could live with a suboptimal plan when the percentage would be more than 10%, cause then the table would be small enough not to matter that much. In turn it has a huge impact to wrongly guess 10% for a huge table... I think the best would be to guess 5% but maximum say 5000. That could work well with both small and huge tables. Maybe those values could be made configurable... just ideas, not like I could implement this... [snip] Cheers, Csaba. ---------------------------(end of broadcast)--------------------------- TIP 2: Don't 'kill -9' the postmaster
